Tina Newman knew what it was. An earthquake. She's been through them before, while touring Universal Studios in California decades ago and then again recently in Costa Rica.

This time, she was in her house on Donzi Drive in Sea Pines. The walls, the ground, the couch she sat on. They shook. Her dog, a Pomeranian mix named Wyly, jumped straight up. It was about 8:30 Thursday morning. The quaking lasted for about 15 seconds or so, Newman reckons.

She called her fiance, who was driving to work.

"Frank, did you feel that?" she said.

He said no and, to Newman's ire, it seemed like he didn't believe her.

So she began a quest.

"I'm not nuts," she said.

Newman knew she couldn't have been the only person in all of Pasco County to feel it. She called the Sheriff's Office. Officers had gotten another call about it.

"I was so happy," she said.

Newman, 66, talked to neighbors and called friends. Some of them felt it, too. Over in Port Richey, a friend's loose change rattled on her kitchen counter.

Then Newman's fiance called back.

"I guess he had been making fun of me," she said, validated, "and then his secretary piped up and said she felt it, too."

But what exactly caused the tremors isn't certain. The National Weather Service station in Tampa Bay hadn't heard anything about it. Don Blakeman, an earthquake analyst at the National Earthquake Information Center out of Colorado, said there definitely was not an earthquake in this part of Florida.

"Florida has the least amount of earthquakes in the United States," Blakeman said. "It almost never happens."

But he didn't deny the rumblings.

"I don't doubt they felt something," he said.

He said it was most likely an explosion or a military plane.

The Pasco County Sheriff's Office sent a bomb squad to Hudson to investigate, but didn't find anything, said spokesman Kevin Doll.

Staff Sgt. Patrice Clarke with MacDill Air Force Base said there are jets flying into Tampa from all over the country for a large air show this weekend.

So that could have been it.

But people who felt the tremor - sliding glass doors rattling, windows vibrating - said they didn't hear any sound; no sonic boom. Nothing.

Newman said there is a mine close to where she lives, but she checked it out and it isn't active. She thought it could have had something to do with the Space Shuttle returning, but it wasn't scheduled for Thursday. She made calls and researched online and now she thinks what happened is this: There were some earthquakes near Puerto Rico and the Virgin Islands, she said, and believes those vibrations traveled and were felt here.

"I know what an earthquake feels like," she said, sticking firm to her story. "This old lady is NOT losing it."